JP2004166570A

JP2004166570A - Method for processing purple sweet potato

Info

Publication number: JP2004166570A
Application number: JP2002335164A
Authority: JP
Inventors: Toshikazu Kuranouchi; 利和藏之内; Makoto Nakatani; 誠中谷; Seiji Tamiya; 誠司田宮
Original assignee: National Agriculture and Bio Oriented Research Organization NARO
Current assignee: National Agriculture and Bio Oriented Research Organization NARO
Priority date: 2002-11-19
Filing date: 2002-11-19
Publication date: 2004-06-17
Anticipated expiration: 2022-11-19
Also published as: JP3671228B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for processing purple sweet potatoes for suppressing change in color even when processing the purple sweet potatoes. <P>SOLUTION: This method for processing the purple sweet potatoes comprises a preliminary treatment for soaking the purple sweet potatoes in an ascorbic acid treating solution at a temperature at the vicinity of the gelatinization temperature of starch contained in the purple sweet potatoes, a steaming process for steaming the purple sweet potatoes after going through the preliminary treatment, and a dry process for drying the steamed purple sweet potatoes. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、紫いもの加工方法に関し、具体的には紫いもを蒸切干しても色調の劣化しにくい加工方法に関する。
【０００２】
【従来の技術】
従来、ジャガイモ、柿等の果菜は、長期保存の目的で切干し加工される場合があり、この際、アスコルビン酸を用いた前処理を行うことにより、変色を防止してその食品の商品価値を損なわれにくくする技術が知られている（特許文献１、２参照）。これは、アスコルビン酸が酸化酵素を不活性化することにより、色素に対する酸化作用が弱くなり、色素の発色が維持されやすくなることによると考えられている。
【０００３】
【特許文献１】
特開平８−２８９７２０号公報
【特許文献１】
特公昭６１−１３７８８号公報
【０００４】
【発明が解決しようとする課題】
しかし、紫いもは、ポリフェノールの一種であるアントシアニン系の色素により、微妙な紫色を呈する独特の色調を持っている。ポリフェノール類は特に酸化作用を受けやすく、これらを多く含有する紫いもは、特に蒸煮・乾燥により変色しやすい。そのため、上述の他の果菜の変色防止方法を紫いもに直接適用しても、製品が著しく黒変したり、色調が暗紫色になったりし、十分な効果を発揮しない場合が多い。
【０００５】
従って、本発明の目的は、上記実情に鑑み、紫いもの加工を行った場合にも、変色を抑制することができる加工方法を提供する点にある。
【０００６】
【課題を解決するための手段】
本発明者らは、上述のアントシアニン等のポリフェノール類が酸化を受けやすいにもかかわらず、紫いもが生澱粉を大量に含むため、酸化防止剤が内部にまで作用することが抑制されていると予想され、その結果、他の果菜に比べて変色防止効果が低下しているものと予想されることを見いだした。そこで、澱粉の物性に着目し、鋭意研究の結果、澱粉の糊化温度近傍においてアスコルビン酸処理を行えば、紫いもの変色を効果的に抑制できることを実験的にみいだし、本発明に想到した。
【０００７】
つまり、前記目的を達成するための本発明の紫いもの加工方法の特徴手段は、紫いもに含まれる澱粉の糊化温度近傍で、前記紫いもをアスコルビン酸処理液に浸漬処理する前処理行程を行った後、
前記前処理行程を経た紫いもを、蒸煮する蒸煮工程を行い、
その蒸煮された紫いもを乾燥する乾燥工程を行う点にある。
【０００８】
ここで、澱粉の糊化温度とは、澱粉の構造により温度の異なるものであって、果菜の種類、品種ごとに微妙に異なる値をとる。また、一つの果菜中に含まれる澱粉にも鎖長などにばらつきがあるため、ある程度の温度域を有する。そのため、本発明でいう糊化温度近傍とは、各紫いもの品種毎に固有の澱粉の糊化温度を調べた場合に、糊化が起こり始める温度から、糊化が明確に始まってしまう温度を含めた温度域を指すものとする。
【０００９】
澱粉の糊化温度近傍でアスコルビン酸を作用させると、そのアスコルビン酸は、糊化しつつある澱粉が吸水するのに伴い、紫いも組織の内部に進入し易くなって、その酸化酵素の失活に役立てられているのではないかと考えられる。そのため、上述の前処理行程を行うことにより、アスコルビン酸が、酸化酵素の作用を抑え、後続の処理中あるいは製品の保存中におけるアントシアニンの酸化を抑制できることになると考えられる。
【００１０】
従って、変色の発生しにくい紫いも加工品を提供できるようになって、食品としての付加価値を高めることができた。また、このような温度は、澱粉の糖化酵素が働きやすい温度でもあるため、紫いもの甘味増加にも寄与し、食品としての付加価値をさらに高められる。
【００１１】
尚、紫いもの加工に際して、皮を除去した紫いも原料をそのまま前処理行程に供してもよく、紫いも原料を切断したものを前処理行程に供してもよい。ここで、切断した後前処理行程を行うと、紫いもの組織全体にアスコルビン酸が迅速に作用するので好ましい。
【００１２】
尚、前記紫いもとして具体的には、パープルスイートロード、種子島紫、九州１３９号から選ばれる少なくとも一種のものは、やや色素量の多い品種であり、商品価値も高く、また、色素の酸化防止を行う上でも意味が大きい。これらの紫いもの生産する澱粉の糊化温度は、それぞれ、７７．４５℃、７１．５５℃、７３．６０℃であり、前記前処理行程が７１℃〜７７℃での糊化温度が紫いもの澱粉の糊化温度として最適値であると考えられる。
【００１３】
また、前記アスコルビン酸処理液が、アスコルビン酸を１〜５％含有するものである場合、色調の改善効果が発揮され、かつ、紫いもが固くなりすぎないことから好ましいことが実験的に見いだされている。また、このときの前記前処理行程時間としては１〜３時間が最適である。
また、前記蒸煮工程が、加熱水蒸気による場合、１〜３時間加熱水蒸気に晒すものであることが好ましい。尚、ここで、加熱水蒸気というものは、水の沸騰によって発生する水蒸気を指し、常圧では１００℃の水蒸気をいう。
また、前記乾燥工程は、室温以下の冷暗所で２〜４日間行うことが好ましく、具体的には１２℃、ＲＨ２０％程度の屋内に３日程度乾燥させることが好ましい。
これらの処理により紫いもは特に蒸切干に加工される際に、変色がおきにくくかつ、硬度もあまり高くならないので、蒸切干紫いもとして高い品質のものを提供できることになる。
【００１４】
【発明の実施の形態】
以下に本発明の実施の形態を図面に基づいて説明する。
本発明の紫いもの加工方法は、図１に示す手順で行われる。
まず、収穫されたパープルスイートロードのいもを洗浄し、剥皮、切断する。切断は、紫いもの両端部を除去したものを縦方向にスライスした。
スライスされた紫いもは、アスコルビン酸処理液に、管理温度７５℃で２時間浸漬される（前処理行程）。
前記アスコルビン酸処理液としては、２ｇ／Ｌのアスコルビン酸を含有する水溶液を用いた。
【００１５】
前記アスコルビン酸処理液から取り出された紫いものスライスは、蒸し器に移され、加熱水蒸気により２時間蒸煮される（蒸煮工程）。
【００１６】
蒸煮された紫いものスライスは、冷暗所（１２℃、２０％ＲＨの屋内）で乾燥させられ、蒸切干紫いもの製品とされる（乾燥工程）。
【００１７】
その結果得られた蒸切干紫いもは、図２に示すように鮮やかな紫色の色調が維持されたものとなり、前記前処理行程におけるアスコルビン酸処理を行わなかったものに比べきわめて商品価値の高いものが得られることがわかった。
【００１８】
【実施例】
以下に本発明の実施例を図面に基づいて説明する。
上述の実施の形態における紫いも種としてパープルスイートロードの他に、種子島紫、九州１３９号を用い、前記前処理行程のアスコルビン酸処理温度を種々変化させた実験を行った。その結果得られた蒸切干紫いもの性状を表１に示す。尚、ここでのべた条件以外は上述の実施の形態のものと同じである。
【００１９】
【表１】

（注）色調・硬度は無処理のものとの差で示している。
【００２０】
表１中の色調はハンター色差計により測定した。Ｌは明度、ａは赤色度、ｂは黄色度を示す。また、硬度は、６ｍｍ径の円柱が表面を貫入するときの力（単位Ｎ）を測定した。表１より、パープルスイートロードでは、蒸切干の明度では差は無いものの、赤色度は７５℃で効果が大きい。また、種子島紫では、明度および赤色度の改善効果が７５℃で大きいことがわかる。また、九州１３９号では、明度の改善効果が７５℃で大きく、８５℃での赤色度の改善効果も大きいが、総合的に考えると明度の改善から７５℃の方が有利と考えられる。
３材料の平均で見ると、明度および赤色度とも、７５℃での効果が大きく、従って、色調は７５℃の処理で改善効果が大きいといえ、糊化温度近傍における前処理が最も好ましいことがわかる。
【００２１】
次に、アスコルビン酸処理を行う場合のアスコルビン酸濃度を種々変更して実験を行った。その結果得られた蒸切干紫いもの性状を表２に示す。尚、ここでのべた条件以外は上述の実施の形態のものと同じである。
【００２２】
【表２】

【００２３】
表２より、いずれの紫いもの場合であっても、アスコルビン酸濃度の増加に伴って蒸切干の硬度が高くなる傾向にあることが読みとれ、特に種子島紫の場合を見ると、５ｇ／Ｌ以下程度が好適であることがわかる。また、アスコルビン酸は１ｇ／Ｌ程度で色調の変化等に影響を与えていることがわかる。つまり、紫いもに対するアスコルビン酸処理の際の濃度は１〜５ｇ／Ｌが好ましいことがわかる。
【図面の簡単な説明】
【図１】紫いも加工方法の手順を示す図
【図２】蒸切干紫いもの形態を示す図[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a processing method for purple violet, and more specifically, to a processing method in which the color tone is hardly deteriorated even when the purple peach is steamed and dried.
[0002]
[Prior art]
Conventionally, fruits and vegetables such as potatoes and persimmons are sometimes cut and dried for the purpose of long-term storage.At this time, pretreatment using ascorbic acid prevents discoloration and reduces the commercial value of the food. There are known techniques for preventing damage (see Patent Documents 1 and 2). This is thought to be due to the fact that ascorbic acid inactivates the oxidase, the oxidizing action on the dye is weakened, and the color development of the dye is easily maintained.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 8-289720 [Patent Document 1]
JP-B-61-13788 [0004]
[Problems to be solved by the invention]
However, purple peach has a unique color tone that exhibits a subtle purple color due to an anthocyanin-based pigment that is a kind of polyphenol. Polyphenols are particularly susceptible to oxidizing action, and purple peaches containing a large amount thereof are particularly liable to change color by steaming and drying. Therefore, even if the above-mentioned other methods for preventing discoloration of fruits and vegetables are directly applied to purple peach, the product is often remarkably blackened or the color tone becomes dark purple, and the effect is often not sufficiently exhibited.
[0005]
Therefore, an object of the present invention is to provide a processing method capable of suppressing discoloration even when a purple object is processed in view of the above situation.
[0006]
[Means for Solving the Problems]
The present inventors have found that despite the fact that polyphenols such as the above-described anthocyanins are susceptible to oxidation, purple peach contains a large amount of raw starch, so that the action of the antioxidant to the inside is suppressed. As a result, it was found that the effect of preventing discoloration was expected to be lower than that of other fruits and vegetables. Therefore, focusing on the physical properties of starch, as a result of intensive research, it has been experimentally found that if ascorbic acid treatment is performed near the gelatinization temperature of starch, discoloration of purple can be effectively suppressed, and the present invention has been reached. .
[0007]
That is, the characteristic means of the method for processing purple violet of the present invention for achieving the above-mentioned object is a pretreatment step of immersing the purple violet in an ascorbic acid treatment solution at around the gelatinization temperature of the starch contained in purple. After doing
Performing a steaming step of steaming the purple peach that has passed through the pretreatment step,
The point is to perform a drying step of drying the steamed purple thigh.
[0008]
Here, the gelatinization temperature of the starch varies depending on the structure of the starch, and takes a slightly different value depending on the type and variety of the fruit and vegetable. In addition, the starch contained in one fruit vegetable also has a certain temperature range because the chain length and the like also vary. Therefore, the vicinity of the gelatinization temperature referred to in the present invention is the temperature at which gelatinization starts clearly from the temperature at which gelatinization starts to occur when the gelatinization temperature of starch specific to each purple variety is examined. Shall mean the temperature range including.
[0009]
When ascorbic acid is allowed to act near the gelatinization temperature of starch, the ascorbic acid becomes easier to penetrate into the purple tissue as the gelatinizing starch absorbs water, and the oxidase is inactivated. It is thought that it was useful. Therefore, it is considered that ascorbic acid can suppress the action of the oxidase and suppress the oxidation of anthocyanin during the subsequent processing or storage of the product by performing the above pretreatment step.
[0010]
Accordingly, it is possible to provide a processed product having a purple color, which is unlikely to cause discoloration, and to increase the added value as food. In addition, such a temperature is also a temperature at which the saccharifying enzyme of starch is easy to work, so that it also contributes to an increase in the sweetness of purple ones, thereby further increasing the added value as food.
[0011]
In processing the purple product, the purple raw material from which the skin has been removed may be directly subjected to the pretreatment step, or the purple raw material cut may be subjected to the pretreatment step. Here, it is preferable to perform a pretreatment step after cutting, because ascorbic acid quickly acts on the entire purple tissue.
[0012]
In addition, specifically, at least one kind selected from purple sweet road, Tanegashima purple, and Kyushu 139 is a variety having a relatively large amount of pigment, having high commercial value, and preventing oxidation of the pigment. It is also significant in performing. The gelatinization temperatures of the starches produced by these purple products are 77.45 ° C., 71.55 ° C., and 73.60 ° C., respectively. It is considered that the gelatinization temperature of potato starch is the optimum value.
[0013]
When the ascorbic acid-treated solution contains 1 to 5% of ascorbic acid, it is experimentally found that the effect of improving the color tone is exhibited, and the purple peach is preferable because it does not become too hard. ing. Further, the pre-processing step time at this time is optimally 1 to 3 hours.
When the steaming step is performed by using heated steam, it is preferable that the steaming step is performed by exposing to heated steam for 1 to 3 hours. Here, the term “heated steam” refers to steam generated by boiling water, and refers to steam at 100 ° C. at normal pressure.
Further, the drying step is preferably performed in a cool and dark place at room temperature or lower for 2 to 4 days. Specifically, it is preferable to dry indoors at 12 ° C. and RH of about 20% for about 3 days.
By these treatments, purple peach is hardly discolored and hardly hardened particularly when processed into steamed dried peach, so that a high quality of steamed dried purple peach can be provided.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
The processing method of the purple thing of the present invention is performed by the procedure shown in FIG.
First, the harvested purple sweet road potatoes are washed, peeled and cut. For cutting, the purple one from which both ends were removed was sliced in the vertical direction.
The sliced purple thigh is immersed in an ascorbic acid-treated solution at a control temperature of 75 ° C. for 2 hours (pretreatment step).
As the ascorbic acid treatment liquid, an aqueous solution containing 2 g / L of ascorbic acid was used.
[0015]
The purple slice taken out from the ascorbic acid-treated solution is transferred to a steamer and steamed with heated steam for 2 hours (steaming step).
[0016]
The steamed purple slice is dried in a cool and dark place (12 ° C., 20% RH indoors) to obtain a steamed dried purple product (drying step).
[0017]
The resulting steamed dried purple peach maintains a vivid purple color tone as shown in FIG. 2 and has a very high commercial value as compared with the one without the ascorbic acid treatment in the pretreatment step. Was obtained.
[0018]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Experiments were carried out in which the temperature of ascorbic acid treatment in the pretreatment step was varied by using Tanegashima Purple and Kyushu 139 in addition to Purple Sweet Road as purple seeds in the above embodiment. The properties of the resulting steamed dried purple are shown in Table 1. The conditions other than the conditions described here are the same as those of the above-described embodiment.
[0019]
[Table 1]

(Note) The color tone and hardness are indicated by the difference from the untreated one.
[0020]
The color tone in Table 1 was measured by a Hunter color difference meter. L indicates lightness, a indicates redness, and b indicates yellowness. The hardness was measured by a force (unit: N) when a cylinder having a diameter of 6 mm penetrated the surface. From Table 1, it can be seen that the red sweetness at 75 ° C. has a significant effect on the purple sweet road, although there is no difference in the brightness of the steamed dried dried seaweed. In addition, in Tanegashima purple, the effect of improving brightness and redness is large at 75 ° C. In Kyushu 139, the effect of improving brightness is large at 75 ° C., and the effect of improving redness at 85 ° C. is also large. However, from a comprehensive viewpoint, 75 ° C. is considered to be more advantageous from the viewpoint of improving brightness.
Looking at the average of the three materials, both the lightness and the redness have a large effect at 75 ° C., and therefore, it can be said that the color tone has a large improvement effect at 75 ° C. The pretreatment near the gelatinization temperature is most preferable. Understand.
[0021]
Next, experiments were carried out with various changes in ascorbic acid concentration when performing ascorbic acid treatment. Table 2 shows the properties of the resulting steamed dried purple. The conditions other than the conditions described here are the same as those of the above-described embodiment.
[0022]
[Table 2]

[0023]
From Table 2, it can be seen that in any case of purple, the hardness of the steamed dried grape tends to increase as the ascorbic acid concentration increases, and especially in the case of Tanegashima purple, it is 5 g / L or less. It turns out that the degree is suitable. In addition, it can be seen that ascorbic acid has an effect of about 1 g / L on a change in color tone and the like. That is, it is found that the concentration of the purple peach during the ascorbic acid treatment is preferably 1 to 5 g / L.
[Brief description of the drawings]
FIG. 1 is a diagram showing a procedure of a purple peach processing method. FIG. 2 is a diagram showing a form of steamed dried violet.

Claims

In the vicinity of the gelatinization temperature of the starch contained in purple peach, after performing a pretreatment step of immersing the purple peach in an ascorbic acid-treated solution,
Performing a steaming step of steaming the purple peach that has passed through the pretreatment step,
A processing method of purple stuff that performs a drying step of drying the steamed purple peach.

2. The method according to claim 1, wherein the purple peach is at least one selected from purple sweet road, Tanegashima purple, and Kyushu 139, and the pretreatment step is performed at 71 ° C. to 77 ° C. 3.

2. The method according to claim 1, wherein the ascorbic acid-treated solution contains 1 to 5% of ascorbic acid, and the pretreatment step is performed for 1 to 3 hours.

2. The purple thing processing method according to claim 1, wherein the steaming step is performed by exposing to a heated steam for 1 to 3 hours.

The method according to claim 1, wherein the drying step is performed in a cool dark place at room temperature or lower for 2 to 4 days.